The ratings of four Chemicals stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

The Mosaic Co. (NYSE:MOS) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Mosaic produces and distributes crop nutrients to the agricultural communities located in North America and other countries. In Portfolio Grader’s specific subcategory of Sales Growth, MOS also gets an F. The stock price has fallen 9.7% over the past month, worse than the 1.7% decrease the S&P 500 has seen over the same period of time. For a full analysis of MOS stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.